Selective and potent GluR5-subunit containing kainate receptor antagonist (apparent KD = 1.09 mM). Displays ~ 90-fold selectivity over AMPA receptors and recombinant human GluR6- and KA2-containing kainate receptors. Has little or no action at NMDA or group I mGlu receptors. Selectively blocks kainate receptor-mediated LTP induction in rat hippocampal mossy fibres. Active enantiomer UBP 302 (Cat. No. 2078) available.